md5($salt.md5($pass)) No crack

Hey everyone,I made the following test:

password:123456
salt:http://www.google.comR1191SOF
hash types: md5($salt.md5($pass))

The password hash:
0666a532923627fb464fc3c4122de58f

The test6.txt:
0666a532923627fb464fc3c4122de58f:http://www.google.comR1191SOF


./oclHashcat64.bin -m 3710 --attack-mode 3 test6.txt --increment --increment-min 6 --increment-max 6 --custom-charset1 ?d ?1?1?1?1?1?1

Carck result:
Session.Name...: oclHashcat
Status.........: Exhausted
Input.Mode.....: Mask (?1?1?1?1?1?1) [6]
Hash.Target....: 0666a532923627fb464fc3c4122de58f:http://www.google.comR1191SOF
Hash.Type......: md5($salt.md5($pass))
Time.Started...: 0 secs
Time.Estimated.: 0 secs
Speed.GPU.#1...: 56227.2 kH/s
Recovered......: 0/1 (0.00%) Digests, 0/1 (0.00%) Salts
Progress.......: 1000000/1000000 (100.00%)
Skipped........: 0/1000000 (0.00%)
Rejected.......: 0/1000000 (0.00%)

No crack,Why?